Doctor Emmett L. Brown refers to himself as "a student of all sciences" and is depicted as a talented inventor. His homes in 1985, 1955, and 1885 are shown to contain various labor-saving gadgets.
He appears to be heavily influenced by scientists of previous eras, naming successive pet dogs Copernicus and Einstein, and having portraits of Isaac Newton, Benjamin Franklin, Thomas Edison and Albert Einstein in his laboratory. His favorite author is Jules Verne and his family name was originally "von Braun" before World War I.
Emmett's family moved to Hill Valley from Germany in 1908. Although initially wealthy because of his inheritance, he spent his entire family fortune on his time travel project. When the Brown mansion was destroyed by fire in 1962 and the property sold to developers, Doc subsequently resided in the mansion's garage. Once broke, he established a privately owned business to offer 24-hour scientific services, building ingenious devices for his customers.
Emmett's work appears to be highly regarded, enough for him to win an award for his work. However, he is shown as absent-minded at times, and various statements by other characters inhabiting Hill Valley indicate that he is generally regarded as strange, eccentric, or insane. Being very loud and sprightly, he often speaks with wide-eyed expressions and broad gestures ("Great Scott!" being one of his well-known catchphrases) and tends to be overly verbose in his delivery, referring in one case to a school dance as a "rhythmic ceremonial ritual".
Doc and Marty met several years prior to the events of the first time travel experiment when Marty, out of curiosity, sneaked into Doc's lab after being warned by his parents to stay away from him. Happy to be revered as 'cool', Doc hired Marty as his part-time lab assistant.
In the original timeline, in contrast with Marty's shy and unassertive father, George McFly, Doc is a supportive and open-minded mentor for Marty. Doc's positive influence in turn allows Marty to mentor George in 1955, which appears to encourage George's later success as a novelist, and help him become a better husband and father. One line in particular, "If you put your mind to it, you can accomplish anything," originates from Doc. Marty repeats it to George in 1955, who repeats it back to Marty in the post time travel 1985.
Doc has been involved with illegal and criminal enterprises (albeit as a means to obtain items for his inventions he could not purchase legally) but he is naive and care-free about the consequences of his actions. He excitedly tells Marty how he cheated Libyan terrorists out of stolen plutonium: "They wanted me to build them a bomb, so I took their plutonium and, in turn, gave them a shoddy bomb casing full of used pinball machine parts!"
Despite being intelligent and logical for the most part, Doc is somewhat naive at times about the unknown possible uses of his time machine, initially actively explores the course of the world's future and tries to alter the past or future of the principal characters to improve their lives. However, events lead him to conclude that time travel is too dangerous for humankind. His conviction initially strengthened when he realizes that he has unwittingly altered history by preventing the death of Clara Clayton in 1885; he concludes that the time machine has "caused nothing but disaster" and asks Marty to destroy it once he returns to his own time. Nonetheless, Doc pursues a romantic relationship with Clara despite the risks of further disrupting the timeline.
However, after having been left behind in 1885 when Marty departs in the DeLorean for 1985, Doc starts a family with Clara; the couple have two sons, Jules and Verne. He eventually builds another time machine out of a steam locomotive, and the Browns return to 1985 in order to pick up Einstein before setting out for another adventure.